The present invention relates to a grinding wheel which is most suitable for polishing of the surface of a complicated shape part of an object to be polished having a complicated shape, as typified by a groove part of a wafer boat, and a polishing method employing it.
For a heat treatment jig for production of a semiconductor as typified by a wafer boat, prevention of slip of a wafer at the time of heat treatment has been an important subject for study. Here, slip (also called xe2x80x9cglidexe2x80x9d or xe2x80x9cdislocationxe2x80x9d) means formation of minute difference of elevation on a wafer due to crystal defects which can be observed by a microscope. Such a slip is considered to occur due to internal stress by the wafer""s own weight or due to heat strain stress based on non-uniformity in the in-plane temperature of the wafer, since it is likely to occur at a part in the vicinity of a part of the wafer which is in contact with the jig, when the wafer is subjected to a heat treatment at a high temperature at a level of 1,000xc2x0 C. for a long period of time for example.
As a countermeasure to prevent occurrence of the slip (hereinafter referred to as slip countermeasure), JP-A-2000-119079 proposes to make the surface roughness Ra at most 0.2 xcexcm at a part on a heat treatment component for a semiconductor made of Sixe2x80x94SiC to be in contact with a Si wafer, and use of a diamond blade as a process therefor also as grooving. However, in the above publication, no specific disclosure is made such as the type of the diamond blade or grooving conditions.
Further, JP-A-2000-124143 proposes to make the vertical distance between the top and the root (corresponding to the surface roughness Ry) on the surface of holding grooves of a boat for heat treatment at most 10 xcexcm, however, no specific means is disclosed.
Further, for a heat treatment jig for production of a semiconductor, in addition to the above slip countermeasure, a countermeasure for high purification is also important. For such a countermeasure for high purification, a chemical vapor deposition method (hereinafter referred to as CVD) may be carried out to form a film (hereinafter referred to as CVD film) on the surface of a substrate of the jig, since 1) such a film is excellent in heat resistance and corrosion resistance, 2) it has an extremely low content of metal impurities, 3) it can suppress diffusion of impurities such as metals in the inside of the substrate into a semiconductor wafer, and 4) it has excellent properties such as denseness.
With respect to such a CVD film, protrusions may form on the surface of the CVD film in some cases although the size and the number vary depending upon synthesis conditions. The protrusions formed on the surface of the CVD film are considered to be a main cause of the slip, and for the slip countermeasure, a method of smoothing the surface of the CVD film to eliminate the protrusions (hereinafter smoothing of the surface is generically referred to as polishing) has been desired.
In a case where the CVD film is formed on a flat plate, polishing is relatively easily carried out. However, no means has been known to polish the surface of a CVD film formed on an object to be polished having a complicated shape such as a groove part of a wafer boat. For example, when a conventional diamond blade is employed as a means of polishing a CVD film formed on a groove part of a wafer boat, a stress is applied to teeth of a comb constituting grooves in a step of applying the blade to the grooves, whereby cracks are likely to form in the vicinity of roots of the teeth of the comb, and if the film thickness is at most 150 xcexcm, the thin CVD film is likely to be peeled off and no desired film thickness may be obtained.
Under these circumstances, it is an object of the present invention to provide a grinding wheel for polishing, which is suitable for polishing the surface of a complicated shape part of an object to be polished having a complicated shape, as typified by a groove part of a wafer boat, and a polishing method employing it.
The present invention provides a grinding wheel for polishing, which comprises a grinding substrate and diamond-containing resin fibers implanted in the substrate in a form of a brush, and a polishing method employing it.
Now, the present invention will be described in detail with reference to the preferred embodiments.